1. Field of the Invention
The present invention relates to a process of producing N-formylaspartic anhydride by reacting aspartic acid with formic acid and acetic anhydride.
2. Description of the Background
A process which is known for the production of N-formylaspartic anhydride involves the reaction of aspartic acid with a large excess of formic acid and acetic anhydride, after which an aromatic hydrocarbon and/or halogenated hydrocarbon is added to the reaction mixture. Product N-formylaspartic anhydride is then isolated from the medium. (Published Unexamined Japanese Patent Application 91210/76). Another process involves the reaction of aspartic acid with formic acid and acetic anhydride in essentially stoichiometric amounts. However, a substantially longer reaction time of 48 to 60 hours is required (Published Unexamined Japanese Patent Application 46279/84).
However, the above described processes are not satisfactory from the industrial viewpoint, because the mother liquor which remains can only be treated with difficulty because of the use of formic acid in large excess amounts, or because an aromatic hydrocarbon and/or halogenated solvent is employed, or because a very prolonged reaction time is required, even though formic acid and acetic anhydride are used as reactants in stoichiometric amounts. A need therefore continues to exist for a method of preparing N-formylaspartic anhydride in improved yields and shorter reaction times.